Electric arc discharge tube



y 23, 1933- w. DE IGROOIT ET AL 1,910,755

ELECTRIC ARC DISCHARGE TUBE Fil ed Oct. 18, 1928 Patented May 23, 1933 UNITED STATES PATENT OFFICE,

WILLEM DE GROOT AND JOHANNES GIJSBERTUS WIL ELI M LLE or EINDHovEN, NETHERLANDS, AssIGNoEs mo N.'V. PHILIPS GLCEILAMPENE DEICKE O EIND- HovEN, NETHERLANDS, A LIMITED LIABILITY COMrA Y, oETH NETHERLANDS ELECTRIC ARC DISCHARGE "TUBE Application filed October is, 1928, Serial No. 313,355, and a the Netherlands November 30,1927.

The invention relates to are discharge tubes comprising an incandescent cathode, preferably a W'ehnelt cathode. In a prior specification Serial No. 162,896, filed January 22nd, 1927, in the name of Bruijnes, Oosterhuis & Mulder, acontinuation of which, Serial No. 555,121 was filed on August 4th, 1931, is described an arc discharge tube filled with a gaseous atmosphere. consisting of a mixture of a rare gas and mercury vapour. Use should preferablybe made of a mixture of argon and mercury vapour. Now the applicants have found that the gaseous filling con tained in an arc discharge tube which com,- prises an incandescent cathode, may contain, in addition to mercury vapour, another gas that is not a rare gas. Use should preferably be made of a filling of mercury vapour and hydrogen or of mercury vapour and nitrogen but also other gases such, forexample ascarbon monoxide or carbon dioxide together with mercury vapour may give good results. In are discharge tubes according to the invention may also be used mixtures of different gases together with mercury vapour. Thus,

for example, use may be made of fillings containing a rare gas, for example a small quantity of argon, in addition to mercury vapour and another gas that is not a rare gas.

The pressure of the gaseous filling should preferably be lowerthan some centimetres of mercury and the distance between the electrodes may be about 1 cm. The value of the arc voltage substantially depends on these two values and principally on their product.

The invention will be more clearly understood by referring to the accompanying drawing which represents diagrammaticallya discharge tube according to the invention which acts as a rectifier. The discharge tube shown, in the drawing comprises a bulb 1 of glass or similar material having hermetically sealed to it a glass tube 2 provided at its end with a pinch in which the supply wires 3 and 4 of a Wehnelt cathode 5 and the supply wires 6 and of anodes 8 or 9 are hermetically sealed. The incandescent cathode is consti- ,tuted by a preferably helically wound wire which is superficially coated with a material adapted to emit a large quantity of electrons at a relatively low temperature, for. example with barium, barium oxide or the oxide of another alkaline earth metal. This cathode may be manufactured by applying barium metal on a core wire, which metal may be subsequently oxidized. Alternately, a core wire may be coated with a paste containing a barium compound which when heated yields the oxide. The cathode preferably consists of a wire of highly refractory metal, for example tungsten, on which a wire of a metal of lower melting point, for example nickel, is helically wound, the body thus produced being subsequently coated with an alkaline earth or an alkaline earth oxide. The anodes 8 and 9 are constituted by plates of nickel, carbon of similar material. In the discharge tube has been volatilized a small quantity of magnesium or an alkaline earth metal which has deposited on the inner wall of the discharge tube. The gaseous filling may consist of mercury vapour and hydrogen. The pressure of the gaseous atmosphere and the distance between the cathode 5 and the anode 7 are so chosen that the tension between the electrodes is as low as possible. In some cases this tension may be smaller than the ionization voltage of the gas. Into the discharge tube has been introduced a small quantity of merc'uryso that the vapour pressure thereof is determined by the temperature of the tube, said temperature being relatively low (under 100 G.). In a particular mode of realization in which the temperature of the Wehnelt cathode is 1000 C. and the pressure of the hydrogen is 0.5 mm. while the distance between the electrodes is about 5 mm. the arc I voltage may be aboutlO to 15 volts.

With lower pressures of the gas or in discharge tubes adapted to rectify high-tension 90 alternating currents the distance between the electrodes may be of the order of some centimetres.

The discharge tube according to the invention is exceedingly Well suited for charging batteries and operates with a higher efficiency than discharge tubes used for similar purposes Which are not in possession of the features set forth in the present specification or in the said prior specification.

What We claim is:

1. An are discharge tube, comprising a VVehnelt cathode, and an anode, the said tube containing liquid mercury, a rare gas, and

a gas other than a rare gas.

2. An arc discharge rectifier tube, comprising a Wehnelt cathode, and an anode, and containing liquid mercury, a rare gas, and a gas other than a rare gas, wherein the distance between the electrodes is of the order of l cm., while the pressure of the gas is of the order of 1 mm. of mercury.

- In testimony whereof We have signed our names to this specification. 25.

WILLEM do GROOT.

JOHANNES GIJSBERTUS WILHELM MULDER. 

